This subproject is one of many research subprojects utilizing the resources provided by a Center grant funded by NIH/NCRR. The subproject and investigator (PI) may have received primary funding from another NIH source, and thus could be represented in other CRISP entries. The institution listed is for the Center, which is not necessarily the institution for the investigator. Protein arginylation is a poorly understood posstranslational modification that is essential for cardiovascular development and angiogenesis and possibly takes part in the normal functioning of other physiological systems and cell types. Evidence indicates that many proteins are arginylated in vivo;however the identity of these proteins is unknown. This collaboration is aimed to identify proteins arginylated in vivo.